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Message-ID: <dfd3823f11ffd2d4c838e961d61ec9ae8a646773.1707080349.git.dxu@dxuuu.xyz>
Date: Sun, 4 Feb 2024 14:06:34 -0700
From: Daniel Xu <dxu@...uu.xyz>
To: andrii@...nel.org,
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ast@...nel.org,
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Cc: martin.lau@...ux.dev,
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linux-kernel@...r.kernel.org
Subject: [PATCH bpf-next v2 1/2] bpf: Have bpf_rdonly_cast() take a const pointer
Since 20d59ee55172 ("libbpf: add bpf_core_cast() macro"), libbpf is now
exporting a const arg version of bpf_rdonly_cast(). This causes the
following conflicting type error when generating kfunc prototypes from
BTF:
In file included from skeleton/pid_iter.bpf.c:5:
/home/dxu/dev/linux/tools/bpf/bpftool/bootstrap/libbpf/include/bpf/bpf_core_read.h:297:14: error: conflicting types for 'bpf_rdonly_cast'
extern void *bpf_rdonly_cast(const void *obj__ign, __u32 btf_id__k) __ksym __weak;
^
/vmlinux.h:135625:14: note: previous declaration is here
extern void *bpf_rdonly_cast(void *obj__ign, u32 btf_id__k) __weak __ksym;
This is b/c the kernel defines bpf_rdonly_cast() with non-const arg.
Since const arg is more permissive and thus backwards compatible, we
change the kernel definition as well to avoid conflicting type errors.
Signed-off-by: Daniel Xu <dxu@...uu.xyz>
---
kernel/bpf/helpers.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 4db1c658254c..3503949b4c1b 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2484,9 +2484,9 @@ __bpf_kfunc void *bpf_cast_to_kern_ctx(void *obj)
return obj;
}
-__bpf_kfunc void *bpf_rdonly_cast(void *obj__ign, u32 btf_id__k)
+__bpf_kfunc void *bpf_rdonly_cast(const void *obj__ign, u32 btf_id__k)
{
- return obj__ign;
+ return (void *)obj__ign;
}
__bpf_kfunc void bpf_rcu_read_lock(void)
--
2.42.1
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